In typical air pumps used in conjunction with aquarium apparatus, a vibrating membrane drives air toward a separator wall dividing the main body of the pump into inner and outer chambers. The separator wall contains a vent valve which comprises a vent hole covered by a flexible valve body which flexes to open and close the vent hole under the force of the vibrating air column. Such vent valves are, for example, described in U.S. Pat. No. 4,099,544 granted to Itakura et al on July 11, 1978.
The valve body of such vent valves typically has a guitar-like shape with a larger rounded base section fixed in a correspondingly shaped seat in the separator wall and connected to a smaller rounded deflectable tongue section which centrally covers the vent hole. A plug member which fixedly retains the larger base section within the seat in the separator wall, has a straight distal edge extending transversely between the base section and the tongue section, against and along which edge the tongue section flexes to open and close the vent hole.
With this guitar-like shape constitution, and specifically the rounded base section, the base can rotate or laterally shift within its seat. Particular care must be taken to properly orient the position of the vent body in its seat on the separator wall so that the tongue section covers the vent hole at all times. Moreover, the flexure of the tongue section toward and away from the separator wall causes a flapping sound as the tongue section strikes the wall upon each closure of the valve. This sound tends to produce a noisy pump and reduces the pleasing effect of the aquarium tank.
Accordingly, it is an object of the present invention to provide a vent valve of an air pump for a fish tank which is virtually noiseless during operation.
Another object is to provide a construction for such vent valve which permits an easy and definitive desired orientation of the valve body relative to the vent hole.